Subject: JEMX Monday meeting 2004-05-24

Participants: NL, SB, JC, CAO, ILR, CBJ, NWJ

1) Status:
   JMX1 has had a gain increase of 12% relative to switch on on early
   March 2004. The preparations for decreasing the HV by 1 step have
   been started.
   
   FM1 (lab model) has recently shown similar gain increase rate which
   is strange because of the higher temperature. The interpretation is
   uncertain (approaching a plateau?)
   
   Gain as a function of count rate is a measure of ageing. Can be tested
   by comparing the gain directly under the calibration sources and in
   the surroundings.
   
2) Future operation:
   Since the rate of ageing is temperature dependent it might be an
   advantage to switch off completely (except the DPE) the dormant
   instrument. This would cool the microstrip plate by ~3.5 degrees
   according to an analysis by Alenia. It is estimated that the lifetime
   of the active detector is prolonged by 25% by this. A small drop of
   gain (~3%) can also be expected. The electronic people at DSRI claim
   that such a switch off is not a problem for the electronics.
   NL will initiate implementing this action - will probably take long
   to evaluate all impacts on the satellite systems (and SPI and IBIS).
   
3) PIF:
   NL has written an technical note that describes the decrease of RMS
   of Crab lightcurve when a number of parameters are varied, in particular
   those describing the collimator shape.
   
   SB has found a strange countrate behaviour when (uncorrected) background
   countrate is plotted against Y (backplane) position, both for energies
   above and below the cut in rejection criteria.
   The dependence on the corrections as well as collimator shape issues
   were discussed in great length and it was decided to continue the
   investigations for determining the position and shape of the collimator.
   
4) Low energy efficiency:
   SB has made a plot of calibration lines + Xe peak as a function of
   (E - E0)/sqrt(E) which should give exactly the same position and shape
   for all lines. Looks fine for all lines except the 5.9 keV calibration
   peaks that fall a little low (width seems OK). Do we see an effect of
   truncation or offset? Continue investigations.
   
5) Munich refereeing done!

6) ISDC activities:
   A couple of IPF files have been lost (040520_0.IPF and 040521_0.IPF)
   and the problem was shown by the ISDC operators to be a full disc
   condition. The occasional instrument team person at ISDC should keep
   an eye on the remaining disc space for the instrument station.
   
AOB: CAO has almost finished the hot spot removal (i.e. setting of event
   status flag). Will be delivered tomorrow.
   
/NJW
   
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Niels J. Westergaard
Danish Space Research Institute
Juliane Maries Vej 30, DK 2100 Copenhagen O
Phone: +45 35 32 57 05; FAX:  +45 35 36 24 75